An ignition device that uses a plasma generation device which radiates an EM (electromagnetic) radiation to the inside of a combustion chamber of an internal combustion engine for generating EM wave plasma is proposed as an ignition device for igniting the internal combustion engine. This kind of ignition device for igniting the internal combustion engine using the plasma generation device is described in JP 2009-38025A1 or JP 2006-132518A1, for example.
In JP 2009-38025A1, a plasma generation device that generates spark discharge in a discharge gap of the spark plug and that radiates microwaves to the discharge gap for enlarging plasma is described. In this plasma generation device, the plasma generated by the spark discharge receives energy from the microwave pulse. The electron in the plasma area is thereby accelerated and the ionizing is promoted to increase the volume of the plasma.
In JP 2006-132518 A1, an ignition device for an internal combustion engine that generates a plasma discharge by radiating EM wave from EM wave device to the combustion chamber is described. An ignition electrode is installed on the upper surface of the piston and is isolated electrically from the piston so that the ignition electrode increases the local EM field intensity in its neighborhood in the combustion chamber. In the ignition device of internal combustion engine, plasma discharge is thereby generated near the ignition electrode.